Pulse producing system



May 13, 1947 A. F. BlscHoFF 2,420,516

PULSE PRODUCING SYSTEM Filed June l5, 1944 3 Sheets-Sheet 2 Figs.

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May 13, 1947. A. F. `BlscHol-'F PULSE PRODUCING SYSTEM Filed Jun 15, 1944 3 Sheets-Sheet 3 Pags D.C. RESTORER NORMAL NORMAL OPERATION TEST Inventor: Alfred F`. Bise hoff,

His Attofney.

Patented May 13, 1947 UNITED S FICE PULSE PRODUCIN G SYSTEM Alfred- F. Bischoff, Milford, Conn., assigner to General Electric Company, a corporation of New York 10 Claims.

l My invention relates to pulse producing systems and it has for one of its objects to provide improved means to produce pulses under accurate control both as to frequency and duration.

Another object of my invention is to provide such a system in which the frequency of the pulses produced is variable while under such accurate control.

A further object of my invention is to provide such a pulse producing system for controlling the deections of the cathode ray device employed in radio location systems of the so-called Loran type. While my invention is not limited to use in such a system, it possesses important advantages when so employed and I shall describe it as applied in such a system.

The novel features which I believe to be characteristic of my invention are set forth with particularity in the appended claims. My invention itself, however, both as to its organization and method of operation, together with further objects and advantages thereof, may best be understood by reference to the accompanying drawings in which' Fig. 1 represents an application of the Loran system; Fig. 2 represents my invention as employed in such a system; Fig.

. 3 Yrepresents certain characteristics pertaining to the invention of Fig. 2; Fig. 4 illustrates the indications produced on the viewing screen of the cathode ray device of Fig. 2; Fig. 5 represents certain details of Fig. 2; and Figs. 6 and 7 represent characteristics pertaining to Fig. 5.

Referring to Fig. 1 of the drawing, I have indicated at l a shore line along which may be located a, plurality oi' radio beacons of which three, designated at 2, 3 and 4, are indicated on the drawing. These beacons are designed to transmit pulses at repetition frequencies of 25, 25116, 252/16, etc., up to 2511s, or more, pulses per second. Each' beacon may include one or more transmitters operating on different ones of these frequencies, each transmitter operating at the same frequency as a transmitter at another sta.- tion and each pair of transmitters operating at the same frequency emitting their pulses in xed phase relation. At 5 I have indicated a ship, for example, having equipment provided in accord with my invention for determining its locaton relative to diierent ones of these beacons. The different stations 2, 3 and 4 are synchronized together so that pulses of, let us say, 25 cycles per second are radiated in xed phase relation from at least two of the stations, as for example stations 2 and 3, and accordingly arrive at the locating equipment 5 in a time phase relation with respect to each other which determines a` locus on which lthe equipment 5 lies. Having determined such a locus the equipment i is then adjusted to receive pulses of a diierent one of the frequencies mentioned which are simultaneously emitted from a dierent pair of stations, as for example stations 3 and 4, thereby determining a second locus. The point of intersection of th'ese loci then determines the Vlocation of the point 5 with respect to the stations 2, 3 and 4.

My present invention has to do with improved means for measuring the time interval between pulses received from a pair of stations 2 and 3 or 3 and 4 and may be described in detail by reference to Fig. 2 when considered in connection with the graphs of Fig. 3.

Referring now to Fig. 2 of the drawing, I have indicated at 6 a source of pulses occurring at, for example, 20 kilocycles per second these pulses being equally spaced apart and each having a negative and a positive peak. 'Ihese pulses are indicated by the curve A of Fig. 3. Th'ese pulses are supplied to a discharge device 1 comprising a pair of diodes one of which has a cathode 8 and an anode 9 and the other of which has a cathode I2 and an anode I3. 'Ihe pulses A are supplied through coupling condenser I4 to the cathode 8 and the anode I3. Th'e anode 9 associated with cathode 8 is grounded directly and the cathode I2 associated with anode I3 is grounded through a condenser I5 of, for example, 0.002 microfarad. The negative pulses of the wave A drive the cathode 8 and anode I3 negative rendering the left-hand diode conductive and the right-hand diode nonconductive. The diode 8, 9, being conductive, prevents the cathode 8 and anode I3 from being varied appreciably negatively with respect to ground and thus the negative peaks are removed and the wave supplied to the diode I2, I3 is thus in the form of the wave B of Fig. 3. The positive pulses of the wave B cause the device I2, I3 to become conducting, caus'ing pulses of current to flow into condenser I5 upon occurrence of each positive peak of the wave A. Thus the condenser I5 charges in stepwise fashion as represented by the curve C of Fig. 3 eachl step being of a predetermined magnitude Vdetermined by the magnitude of the positive pulses of the wave A.

Discharge device I6 operates to discharge condenser l5 after each ten charging steps of the wave C, or after each ten positive pulses of the wave A. Normally this deviceis nonconducting because of potential produced between its cathode and ground by current flowing from a source of operating potential indicated at 38 through resistances I1, I8 and I9 to ground and thence to the negative terminal of the source, the resistances I8 and I9 being connected in series between the cathode of device I6 and ground and being shunted by a bypass condenser 22. The anode of device I6 is connected to the positive terminal of the source of operating potential 38 through the primary winding 23 of a transformer the secondary winding 24 of which is connected between the control electrode 25 and the positive terminal of the condenser I5, this latter winding being shunted by a resistance 26.

When condenser I has reached a charge sufiicient to render the grid 25 positive with respect to the cathode of device I6, current is initiated in winding 23. This current induces a voltage in winding 24 which in turn increases the positive voltage on the grid 25 thereby rendering device I6 more conductive and increasing the current in the winding 23. This action is accumulative and renders the grid 25 sufficiently positive with respect to the cathode completely and rapidly to discharge condenser I5 through the grid to cathode space of device I6 and, in fact, to charge it to a certain extent in the opposite direction as indicated by the portions 21 of the curve C of Fig. 3. This negative charge, however, quickly leaks oil to ground through the diodes of discharge device 1. Condenser I5 then again begins charging from a fixed zero value in its stepwise fashion as represented by the curve C of Fig. 3, this operation repeating continuously.

Upon each discharge of condenser I5 a pulse is produced on the anode of the device I6 as represented by the curve D of Fig. 3, these pulses occurring at 2 kilocycles per second. These pulses are supplied to a chain of frequency dividers 28 and 29, and they are also supplied over conductors 32 and 33 to a clipper amplier 34 and over conductors 32 and 56 to a diode 51 presently to be referred to. The frequency dividers 28 and 29 reduce the frequency of these pulses to 50 pulses per second, the divider 28 dividing its input frequency by 5 and the divider 29 dividing its input frequency by 8, and thus at the output of the divider 29 appears the wave E of Fig. 3 having pulses therein occurring at 50 pulses per second and spaced 2,000 microseconds apart.

It will now be noted that different curves of Fig. 3 have different time bases, the elapse of time in certain instances being indicated by the dotted portions of the curves and in other instances by breaks, as in the cases of curves M and C'.

These pulses of curve E are employed to trigger a multivibrator 35. This multivibrator comprises a pair of discharge devices 36 and 31 the cathodes of which are connected to the point between two resistors 39 and 42 which are connected in series across the source of operating potential 38 and the anodes of which are connected through anode resistors 43 and 44 to the positive terminal of the source of operating potential. Each anode is also connected through a respective resistance 45 and 46 to the control electrode of the opposite discharge device, each of these latter resistances being shunted by respective condensers 41 and 48. The control electrode of device 36 is connected to the negative terminal of the source of operating potential through a resistance 49 and also to the anode of a diode 52 the cathode of which is connected to the negative terminal of the source of operating potential through a resistance 53.

'I'he 50cycle pulses from the output oiV the frequency divider 29 are supplied to resistance 53 through condenser 54 and resistance 55. Of course, the positive peaks of these pulses have no effect upon the diode 52 since they merely drive the cathode positive with respect to the anode. The negative pulses, however, render the diode conductive, producing potential on resistance 49 which drives the control electr-ode of device 36 negative. 'I'hus if device 36 be conductive current therein is reduced causing its anode potential to rise and rendering the control electrode of device 31 less negative with respect to its cathode sufficiently to render that device conductive. When that4 device becomes conductive its anode potential drops forcing the control electrode of device 36 more negative. This action is accumulative, the device 36 rapidly becoming nonconductive and the device 31 becoming conductive. 'I'his latter condition of the multivibrator 35 is maintained until one of the 2- kilocycle pulses of wave D is supplied from conductor 32 over conductor 56 and diode 51 to the control electrode of device 31. Diode 51 operates in exactly the same way as did diode '52 to cause the multivibrator to return to its original condition, discharge device 36 becoming conductive and discharge device 31 becoming nonconductive. In this way a pulse wave is produced on the anode of device 36 indicated at F in Fig. 3, and a similar wave of opposite polarity is produced on the anode of device 31 this latter wave being indicated at G in Fig. 3. is,

It will be observed that the positive pulses of wave F occur at the 50cycle frequency each of these pulses being initiated upon occurrence of one of the pulses of the wave E, these pulses occurring at the rate of 50 per second.' Each positive pulse of wave F continues until the occurrence of the next pulse of wave D, which is 500 microseconds later the wave D being of the frequency of 2 kilocycles. Thus each positive pulse of wave F and each negative pulse of wave G is of substantially 500 microseconds duration these pulses being spaced apart by 19,500 microseconds.

Of course, if no time delay were involved in transmission of pulses through frequency dividers 28 and 29, a pulse of wave E would appear on one control electrode of multivibrator 35 simultaneously with a pulse of wave D on the other control electrode. These pulses might counteract each other and an output pulse of the multivibrator would not be produced. Actually delay is present in the frequency dividers in excess of that in the channels 32 and 56 with the result that this counteraction does not occur. A pulse of wave G is initiated by pulses of wave E and these pulses are terminated by the next pulse of wave D with the result that the positive pulses of wave F and the negative pulses of wave G are slightly shorter than the interval between pulses of wave D by the amount of the delay in the frequency dividers. This delay is of the order of from one to seven microseconds.

The 50cycle pulse wave F is supplied through a differentiator circuit comprising condenser 58 and resistance 59 to the cathode of a diode 62. This differentlator produces sharp negative pulses represented by the wave H of Fig. 3. 'I'hese negative pulses render the diode 62 conductive and trigger a square wave multivibrator 63 Just as did the pulses through diodes 52 or 51 trigger the multivibrator 35. Multivibrator 63 Imerates to produce the two square waves I and J shown in Fig. 3, both of 25 cycles frequency, the wave I being supplied to a xed delay multivibrator 84 and the wave J being supplied to a variable delay multivibrator 85. The variable delay multivi- -bratcr 85 produces pulses represented by the wave K of Fig. 3 these pulses being of positive polarity, 25 per second, and each pulse being initiated upon initiation of a negative pulse of the wave J or on occurrence of a negative pulse o1' the wave H and being of a duration which may be manually varied from essentially zero to 19,500 microseconds as indicated by the arrows 86 on the wave K or Fig. 3 and by the arrow 81 in the rectangle representing multivibrator 65 in Fig. 2. The fixed delay multivibrator 84 produces the positive pulses of wave L, each of which is initiated upon initiation of a. negative pulse' of the wave I. these pulses oi.' wave L being of xed duration as represented by the wave L of Fig. 3 and. of course. occurring at a frequency of 25 per second.

The output of the two multivibrators 64 and 85 are combined and supplied to the pedestal maker 88. This pedestal maker 68fcomprises a multivibrator capable of producing positive pulses of flxed duration each of which is initiated upon termination of one of the positive pulses voi either Wave K or wave L. These positive square wave pulses, or pedestals, are indicated at 88 and 12 in the wave M of Fig. 3. The pedestals 88 are initiated upon termination of the positive pulses of ,the wave K which latter pulses are of variable duration. Thus these latter pulses may be moved either to the left or to the right, i. e., advanced or retarded in time, through a desired range in accord with the time when the positive pulses of the wave K terminate. The pulses 12 of the wave M are xed in time position since they occur upon termination of the positive pulses of wave L, which are of xed duration. These pedestals are supplied to the upper plate 18 of the vertical deecting plates 13 and 14 of a cathode ray device 15.

This device 15 has horizontal deiiecting plates 18, which are connected to the output oi a sweep generator 11, which is synchronized by the square wave pulses from the anode of device 31, these pulses being the 50-cycle pulses of the wave G. This sawtooth generator 11 generates waves of the type indicated at N in Fig. 3. This wave N comprises positive voltage pulses, which are initiated upon each negative pulse of the wave G and the voltage of which continues with constant value throughout the duration of the respective negative pulse of wave G and then linearly reduces as indicated at 18 on the wave N throughout the period between the positive pulses of the wave G. thereby comprising the sawtooth sweep wave N of Fig. 3. Thus the cathode ray of device 15 is swept across the screen during the 19,500- microsecond interval between the negative pulses oi the wave G. It is then brought back to its starting point and held in position during the next negative pulse of the wave G and until the next sweep interval.

Thus during each alternate sweep interval 18 of the wave N one of the pedestals 68 occurs at a. time dependent upon the adjustment oi the multivibrator 85. During the intermediate sweep intervals 18 of the wave N a pedestal 12 of th wave M occurs Vat a iixed time therein.

These alternate and intermediate sweep intervals 'I8 and 18 of the wave N produce separate traces 82 and 88 on the cathode ray screen owing to the fact that thc z5-cycle wave I is also supplied !rom the multivibrator 88 over conductor 84 to one of the vertical deilecting plates 13, 14 or the cathode ray device. Thus the pedestal 89 appears on the lower trace of the cathode ray device at a point thereon which is variable by variation of multivibrator 85, and the pedestal 12 appears on the upper trace 88 on the viewing screen of the cathode ray device at a ilxed position. The ray is thus swept over each trace 25 times per second and over the two traces alternately and is deected from the respective traces by the respective pedestal pulses 88 and 12.

As previously stated, the 20,000-cyc1e pulses of wave A and the 2,000-cyc1e pulses of the wave D are supplied to the amplier and clipper 34 where they are combined and supplied over conductor 84 to the vertical deiectlng plates of the cathode ray device, producing the additional vertical deflections noted in Fig. 4 on the upper and lower traces 82 and 83. These traces are shown in expanded form in Fig. 4 where the pedestal 89 appears on the lower trace 82 and the pedestal 'l2 appears on the upper trace 83 and where the deections 85, 86 and 81 produced by the wave supplied over conductor 86 are also shown. 'Ihese deiiections comprise a time scale, or calibration, on each of the horizontal traces across the viewing screen of the cathode ray device. The ner calibrations 81 are produced by the 20,000-cycle pulsesand occur 50 microseconds apart on the time scale. The deflections 86 oi intermediate length are produced by the 2,000-cycle pulses and occur 500 microseconds apart. The longer deflections are produced by the 40o-cycle pulses from frequency divider 28 and occur 2500 microseconds apart. These latter are supplied from divider 28 to clipper amplifier 34 over circuit 40.

At the right-hand portion of Fig. 2 is shown a receiving antenna 85 connected to a receiver 86' for receiving pulses from the diilerent stations 2, 8, 4, etc. 'Ihese pulses are reproduced in the output circuit 81' of this receiver and are supplied between the vertical deflection plates 13 and 14 of the cathode ray device. If these pulses are received from stations from which they are radiated synchronously at the 25-cyc1e frequency, the pulse from one station produces a stationary vertical deiiection such as that indicated at 88 in Fig. 4 on the upper trace of the cathode ray screen and the pulse from the other station produces a deilection such as that indicated at 89 on the lower trace of the cathode ray screen, these pulses being spaced apart by an amount dependent upon the phase relation between the periodic pulses received from the two stations, that is, by a. time interval dependent upon the position of the receiver. The desired locus is determined from this time interval.

Received pulses of any of the other frequencies transmitted by other parts of the transmitting stations produce indications on the screen which are readily distinguishable from the desired indications, since, being of a frequency diierent from the sweep frequency of the cathode ray device. the deflections of the ray produced thereby do not repeatedly occur at the same position on the screen and therefore appear to move through the picture and are neglected by the observer.

To determine the time interval between receipt of pulses producing the deflections indicated at 88 and 89, the operator iirst adjusts the phase relation of the sweep wave N producing the hori` zontal traces to bring the deection 88 to a point near .the left-hand edge of the pedestal 'I2 as indicated at 92. In doing this the deflection 89 moves to the left by an equal amount and appears at 93. He then adjusts the multivibrator 85 to move the pedestal 58 to a position on its trace such that the deflection 99 agrees in position thereon with the position of the deflection 92 on the pedestal 11.v This agreement is indicated by the dotted lines 59' and 93'. The time interval between the receipt of the two pulses, which is the criterion from which the locus may be determined, is then indicated by the distance between the left-hand edge of the two pedestals this distance being indicated at X on Fig. 4 of the drawing.

The adjustment of the time relation between the wave N, which produces the traces. and the received pulses is controlled by a feedback connection comprising condenser 95 and a pair of diodes 95 and 91 through which the pulses of the 50-cycle wave E, which appear at the output of the frequency divider 29, are supplied back to the condenser I5. 'Ihe magnitude of these pulses is varied by variation of the capacitance of condenser 95, The negative peaks of the pulses render the cathode of diode 95 negative with respect to the anode and thus these negative peaks are short circuited through this diode and are not transmitted through diode 91, The positive peaks produce current in diode 91 charging the condenser I5 to a value dependent upon the adjustment of the condenser '95.

Let us suppose, for example, that the wave E is fed back with sufiicient intensity to produce a charge in condenser I5 equal to that produced therein by iive pulses from source 5 through diode I3, I2. Then following each pulse of wave E, only iive pulses of wave B through diode I3, I2 are required to bring about the discharge operation of device I previously described. Thus the voltage wave on condenser I is that indicated at C' this wave being exactly the same as the wave C except that the portions thereof immediately following each pulse of wave E are shorter and include only ve of the vertical portions' of the step-shaped wave C', and the remaining portions of the wave between pulses of wave E are, therefore, advanced in phase. This means thata. pulse .wave of the character indicated at D' now appears on the anode of the device I0 the pulses thereof agreeing in time with the negative pulses 21 of the wave C'. 4The time interval between each pulse |03 and the next succeeding pulse I02 is shortened by 250 micro-seconds. The spacing of the pulses of the wave D' between pulses I02 and between the last pulse I02 and the following pulse |03 thereof is exactly the same as the spacing of the pulses of the wave D, but each pulse occurs at a shorter interval after the previous pulse designated |03. Accordingly ali of the pulses |02 of wave D', to and including pulses |03. are advanced or retarded in phase by an amount dependent upon the adjustment of the condenser 95.

Mechanical means, not shown, may be provided on this condenser 95 whereby it may be adjusted to any one of nine predetermined values of capacitance thereby in each position to determine the amount that the interval between pulses |03 and subsequent pulses |02 is shortened relative to the' corresponding interval of the wave D. Thus in one position ofthe condenser this interval may be shortened by one step of the wave C. In other positions it may be shortened by 2, 3, 4 up to 9 steps of the wave C.

This new wave D' is transmitted through the frequency dividers 28 and 29 by which it is divided in frequency by 40 and produces in the output of divider 29 the wave E'. 'Ihis wave E' is now of higher frequency than the wave E because the period between successive pulses has now been shortened by 5 steps of the wave C and is thus of 19,750 microseconds lduration or the wave has a frequency of about 251; cycles per second.

The wave E is supplied through diode 52 to discharge device 36 of multivibrator 35 and the wave D is supplied over conductors 32 and 56 and through' diode 51 to discharge device 31 of multivibrator 35. 'I'his multivibrator now produces waves as indicated at F' and G.

The positive pulses of the wave F' and the negative pulses of the wave G' are now shortened with respect to the corresponding portions of waves F and G as indicated in Fig. 3 and hence the sweep periods 19 and 19 of the sweep wave N, which are still of the same duration, are moved to the left or advanced in time as indicated by the wave N' thereby advancing the phase of the wave H as indicated at H.

Of course, since wave H' is advanced in time relative to wave H, al1 of the remaining waves I, J, K, L and M are advanced in time by equal amounts. These remaining waves are not illustrated in their phase advanced position but they have the same relation to wave H as was previously described with reference to wave H.

Thus by momentarily injecting feedback from the output of divider 29 to condenser I5 by momentarily increasing the capacity of condenser 95 to one of its 9 fixed values, the horizontal deflections of the cathode ray may be momentarily advanced to cause thetwo vertical deiiections 98 and 89 produced by received pulses to occur at any desired position on the respective horizontal traces these later deflections of course remaining spaced apart by an amount dependent upon the phase relation between the pulses producing them.

The operator thus manipulates condenser 95 until the deflection 88 appears at the left edge of pedestal 69 as indicated at 92. Of course the deection 89 moves to the left by an equal amount and appears at 93.

Now the operator desires to move pedestal 12 to the same space relationship to deection 93 that he has produced between pedestal 69 and deflection 92. This he does by varying delay multivibrator 55 thereby varying the length of the positive pulses of wave K and thus advancing or delaying the occurrence of the pulses 59 until the desired space relation is produced, i. e., until pedestal 59 appears at position 59' on the screen with deflection 93 appearing at its left edge as indicated at 93'. Then the distance X between the leading edges of the two pedestals is a criterion of the time between the two received periodic pulses and determines the locus on which the receiving station 5 lies.

Now it will be seen that the frequency of the waves I, J, K, L and M may be varied by variation of the position of condenser 95 to equal the frequency of any pair of the shore transmitters 2, 3, 4, etc. The operator therefore varies condenser 95-until another pair of vertical deflections, such as 89, 89, appears on the traces and remains stationary. He then proceeds exactly as described to determine a new locus with respect to two other stationstransmitting pulses at a frequency dilerent from 25 pulses per secandere 9 ond on which his receiver lies. He is now' in position to determine his location with respect to the three stations from which he has received pulses.

In Fig. is uiustratea certain of the details of adjustments of the condenser 95. The switches are illustrated in their right-hand position for such testing purposes, the stair step representation |04 appearing on the viewing screen.

During the normal operation. to determine th'e location oi' the equipment with respect tothe beacon stations previously described the switches |02 and |03 are in their left-hand position. The wave G is then applied through the switch |02 and condenser |05 to the suppressor electrode of a pentode amplier |03 the suppressor of which is connected to the cathode through a resistance |01 and a diode |08 in parallel. Due to the restorer action of the diode |08 and resistance |01, the form of the wave G is somewhat altered as indicated by the wave O in Fig. 7 as impressed on the suppressor grid of the pentode amplifier. The anode of the ampliier |06 is connected through a resistance |09 to the positive terminal oi the source of operating potential the negative terminal of which is connected to the cath'- ode. Its anode is also connected through a condenser ||2 to the control electrode ||3 thereof. This control electrode is also connected through a resistance ||4 to a. variable tap I5 on a potentiometer I6 across the source of anode operatpositive and the pentode tends to pass current."

The resultant drop in voltage on the anode, however, drives the grid ||3 negative tending to reduce the drop in voltage on the anode. The condenser, however, gradually discharges through resistances lil and |09 to produce on the anode of the device |09 the portion of the wave P indicated at IIB. Thus the anode voltage of device |00 varies in accord with the wave P of Fig. '7.

This curve P is the curve N of Fig, 3 drawn-to somewhat different scale. 'I'he voltage represented by the curve N, or the Wave P, on the anode of device 3 is supplied through a paraphase amplifier |20 whereby it is converted to voltages balanced with respect to a iixed mean voltage, which balanced voltages are applied between the horizontal deecting electrodes 16 of the cathode ray device. 0f course, during the deflection period I I8 the vertical deflection voltages are supplied through switch |03 in its lefthand position to the vertical deecting electrode 13 to produce the indications represented in Fig. 4.

The wave O is also supplied through a direct The concurrent restorer |22 to the control electrode |23 of the cathode ray device to interrupt the cathode ray during the negative portions of the wave O and to turn it on during the positive portions oi the wave O. Thus the wave is on during the sweep portions of the wave P and it is of during the portion of the wave P corresponding to the negative pulses of the wave 0.

When switches |02and |03 are at the right, as shown, the volta/ge which appears on condenser |5 oi Fig. 2 is supplied through the switch |03 to the vertical deecting electrode 13 of the cathode ray device. It is desired to observe this voltage during the positive pulses of the waves F and F', which correspond in duration to various adjustments of the capacitance of the condenser 95. Accordingly the wave For F', as the case may be, is supplied through the switch'l02 and condenser |05 to the suppressor electrode of the device |06.

Fig. 6 represents 1the characteristics corresponding to the curves G, O and P with the switches at the right. Under this test condition the wave F is applied through the condenser |05 to the suppressor electrode of the device |06 and to the anode of the diode |08. During the positive pulses of the wave A, current ows in the diode and in the resistance |01' charging condenser |05 negatively with the result that on termination of the positive pulse of the'wave F the suppressor grid is driven strongly negative, as indicated by the negative peaks |24 of the wave O'. This negative portion oi.' the wave maintains the discharge device |06 nonconducting. During the positive portion oi the wave O' the device |06 passes current. Its anode tends to drop in potential but is retarded by reason of the degenerative action previously described of condenser ||2 on the control electrode H3 with 'the result that the anode potential drops gradually, as indicated by the portion |25 of the curve P'. In this way the sawtooth wave P' is` produced on the anode of the device and is supplied through the paraphase amplier |20 between the horizontal deecting electrodes 16. The wave O' is also supplied through the D. C. restorer |22 to turn the rayof the cathode ray device on during the periods |25 oi the sawtooth wave P. This period is, of course, of varying lengthV dependent upon the adjustment of the condenser and thus permits the stair step representation of the voltage of condenser l5 on the viewing screen of cathode ray device 15 as indicated at |04. This stair step wave representation may of course comprise any number of steps from one to ten dependent upon the adjustment of condenser 95.

While I have illustrated a particular embodiment of my invention, it will of course be understood that I do not wish to be limited thereto since various modications both in the circuit arrangement and in the instrumentaiitiesemployed may be made, and I contemplate by the appended claims to cover any such modifications as fallwithin the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. In combination, a pair of electron discharge devices, a, trigger circuit therefor including means responsive to variation in current in either device to produce opposite variation in current in the other device whereby the two devices are alternately actuated between conductive condition and nonconductive condition with trigger andere 11 action, a source of high frequency pulses, a frequency divider, means to supply said high frequency pulses to one of said devices through said frequency divider and to the other devices di rectly lboth to produce current in the respective device in the same sense whereby said devices are triggered from one of said conditions to the other at the frequency appearing at the output oi' said divider, and pulses are produced in each device having the duration of the period between two succemive pulses oi' said high frequency source.

2. In combination, a pair of electron discharge devices, a trigger v circuit therefor including means responsive to variation in current in either device to produce opposite variation in current in the other device whereby the two devices are alternately actuated between conductive condition and nonconductive condition with trigger action, a source of high frequency pulses, a frequency divider, means to supply said high frequency pulses to one of said devices through said -frequency divider and to the other devices directly both to produce current in the respective device in the same sense whereby said devices are triggered from one of said conditions to the other at the frequency appearing at the output of said divider, and pulses are produced in each device having the duration oi' the period between two successive pulses of said high frequency source, and means to vary the duration of said period.

3. In combination, a source of high frequency pulses, a frequency divider, means to supply said high frequency pulses through said divider to produce low frequency pulses, a trigger circuit having an output circuit, means to supply both said high frequency pulses land said low frequency pulses to said trigger circuit, said trigger circuit including means to initiate a pulse in said output circuit in response to each of said low frequency pulses and to terminate each of said pulses in response to the next to occur pulse of said high frequency pulses whereby the duration of each pulse initiated by said trigger circuit is dependent on the time interval between the low frequency pulse in response to which it is initiated and said next to occur pulse of said high frequency pulses.

4. In combination, a source of high frequency pulses, a source of low frequency pulses, a trigger circuit having an output circuit, means to supply both said high frequency pulses and said low frequency pulses t said trigger circuit, said trigger circuit including means to initiate a pulse in said output circuit in response to each of said low frequency pulses, and means to terminate said pulse in said output circuit in response to the next one to occur of said high frequency pulses whereby a succession of pulses having said low frequency are produced in said output circuit each pulse of said succession having a duration dependent upon the time between the respective low frequency pulse and the next high frequency pulse.

5. In combination, a source of high frequency pulses, a source of low frequency pulses having variable time relation to said high frequency pulses, a trigger circuit having an output circuit, means to supply both said high frequency pulses and said low frequency pulses to said trigger circuit, said trigger circuit including means to indi cate a pulse in said output circuit in response to each of said low frequency pulses, and means to terminate said pulse in said output circuit in response to the next one to occur of said high frequency pulses whereby a succession of pulses are produced in said output circuit, each pulse of the succession being initiated in response to a corresponding one of said low frequency pulses and being terminated in response to the next one to occur of said high frequency pulses.

6. In combination, a source of high frequency pulses, a source of low frequency pulses, a trigger circuit having an output circuit, means to supply both said high frequency pulses and said low frequency pulses to said trigger circuit, said trigger circuit including means to initiate a pulse in said output circuit in response to each of said low frequency pulses, means to terminate said pulse in said output circuit in response to the next one to occur of said high frequency pulses wherebyl a succession of pulses having said low frequency are produced in said output circuit each having a duration dependent upon the time between the respective low frequency pulse and the next high frequency pulse, and means to maintain a harmonic relation between said hlgh'and low frequency pulses.

7. In combination, a multivibrator comprising a pair of electron discharge devices, a source of periodic pulses, a frequency divider, means to supply pulses from said source to one of said devices and to supply pulses from said source through said frequency divider to the other of said devices, said multivibrator being constructed and arranged to be operated to one condition of conductivity of said devices in response to pulses from said frequency divider and to be operated to another condition of conductivity in response to pulses from said source directly, and an output circuit connected between the cathode and anode of one of said devices whereby pulses are produced in said output circuit having the frequency oi.' the output of said divider and having duration corresponding to the period of the pulse wave produced by said source of periodic pulses.

8. In combination, a cathode ray device having a viewing screen, a source of periodic pulses, a frequency divider, a multivibrator constructed and arranged to be operated to either of two alternative conditions of conductivity, means to supply pulsesl from said source through said frequency divider to said multivibrator to operate it to one of said conditions and to supply said pulses to said multivibrator directly to operate it to the other of said conditions whereby a pulse wave having the frequency of the output of said divider and having pulses of length substantially equal to the period between pulses of said source is produced in said output, means to deect the ray oi said device over a predetermined path on said screen at the frequency of'said pulse wave and during the periods between said pulses and to deflect it from said path at a frequency of half that of said pulse wave whereby two traces are produced on said screen, and means to modulate each trace at a time therein corresponding to occurrence of a respective phenomenon periodically recurring at half the frequency of said pulse wave, whereby the phase relation between said periodically recurring phenomena may be observed from said screen.

9. In combination, a cathode ray device having a viewing screen, a source of periodic pulses, a frequency divider, a multivibrator constructed and arranged to be operated to either of two alternative conditions of conductivity, means to supply pulsesfrom said source through said divider to said multivibrator to operate it to one of said conditions and to supply said pulses to 13 said multivibrator directly to operate it to the other of said conditions whereby a pulse wave having the frequency of the output of said divider is produced by said multivibrator, means to deilect the ray of said cathode ray device over said screen in a desired direction at the frequency of said pulse wave and to deect it from said direction at half said frequency whereby two traces are produced on sai'd screen, and means to modulate said ray during each trace at a time therein corresponding to occurrence of a respective phenomenon periodically recurring at said half frequency, whereby the phase relation between said periodically recurring phenomena may be observed from said screen.

10. In combination, a cathode ray device having a viewing screen, a frequency divider, a multivibrator comprising a pair of discharge devices arranged to be conducting alternately, means to supply periodic pulses through said divider to one of said devices to alter the condition of conductivity of both of said devices and to supply said pulses to the other of said devices directly to restore said condition of conductivity, whereby a pulse wave is produced at the output of Asaid multivibrator having the frequency of the output of said multivibrator, means to deect the ray of said device across said screen in a desired direction at the frequency of said pulse wave and to deect it at right angles to said direction at half said frequency whereby two traces are pro- REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 2,368,448 Cook Jan. 30, 1945 2,286,894 Browne et al. June 16, 1942 2,314,920 Bumstead Mar. 30, 1943 2,250,819 Wolf July 29, 1941 2,231,591 Pieplow Feb. 11. 1941 2,121,359 Luck et al. June 21, 1938 FOREIGN PATENTS Number Country Date Great Britain Aug. 8, 1939 Certificate of Correction Patent No, 2,420,516.

May 13, 1947.

ALFRED F. BISCHOFF It is hereby certified that errors appear in the printed specification of the above numbered patent requiring correction as follows: Column 6, line 62, for the Word parts read pairs; column 14, line 4, claim l0, after modulation insert during; and that the said Letters Patent should be read With these corrections therein that the same may conform to the record of the Icase in the Patent Office.

, Signed and sealed this 8th day of July, A. D. 1947.

[SEAL] LESLIE FRAZER,

First Assistant Gommz'ssoner of Patents. 

